Regenerative heat exchanger for gas turbines



Feb. 7, 1961 E. T. LINDEROTH REGENERATIVE HEAT EXCHANGER FOR GASTURBINE-S Original Filed Sept. 10, 1953 4 Sheets-Sheet 1 GAS 5/05 All?5/05 FIG. I I v4b E H A7 l COMPRE$$0R EXCHgNGEI-F QZffigg TURBINE i All?7 All? COOLER HEATER 4!) PRESSURE Q 0 550 a c.

.INVENTOR.

VOLUME FIG.

:1, ERIK TORVALD LlNDEROTH MHM ATTORNEY Feb. 7, 1961 E. T. LINDEROTH2,970,815

REGENERATIVE HEAT EXCHANGER FOR GAS TURBINES Original Filed Sept. 10,1953 4 Sheets-Sheet 2 --I;IIII....'

F I G 6 IN VEN TOR.

ERIK TORVALD LINDEROTH Ml q M ATTORNEY.

Feb. 7, 1961 E. T. LINDEROTH 2,970,815

REGENERATIVE HEAT EXCHANGER FOR GAS TURBINES Original Filed Sept. 10,1953 4 heets-Sheet 3 I VENTO K TORV LINDE H ATTORNEY Feb. 7, 1961 E. 'r.LINDEROTH 2,970,315

REGENERATIVE HEAT EXCHANGER FOR GAS TURBINES Original Filed Sept. 10,1953 4 Sheets-Sheet 4 IOO ' Efficiency I I 1 l l 0 IO 20 3O 4O 5O 6O 7O8O 90 I00 FIG. 8

INVEN TOR. ERIK TORVALD LINDEROTH BY M ATTORNEY .horsepower of theoutput of the turbine.

United States Patent() ice REGENERATIVE HEAT EXCHANGER FOR GAS TURBINESErik Torvald Linderoth, N. Malarstrand 60, Stockholm, Sweden Originalapplication Sept. 10, 1953, Ser. No. 379,352,

new Patent No. 2,836,398, dated May 27, 1958. Divided and thisapplication May 7, 1958, Ser. No. 739,450

5 Claims. (Cl. 257269) The present invention relates to regenerativeheat exchangers for transferring heat between two gaseous media,particularly to heat exchangers for gas turbines.

Gas turbines may be operated in an open system or in a closed system.With either system, the heat exchanger serves to transfer the heat ofthe exhaust gases of the turbine to the air fed to the turbine for thepurpose of preheating the air.

The principal object of the present invention is to provide a novel andimproved heat exchanger design which has a coefiicient of efiiciencymuch higher than is attainable with heat exchangers as hitherto known.Calculations and tests have shown that a heat exchanger according to theinvention is capable of attaining an efficiency of 90 percent. A gasturbine associated with a heat exchanger of such a high efiiciency willobtain a fuel economy appreciably superior to that of other heat poweredengines including diesel engines.

Another object of the invention is to provide a novel and improved heatexchanger design which permits to attain the aforesaid high coefficientof eiiiciency with a heat exchanger that is comparatively small andinexpensive. With heat exchangers and gas turbines as hitherto known andwhich are similar in design to those employed in connection with steampower plants, the aforesaid high efficiency is very diflicult to obtainand, if obtained at all only at the expense of extreme bulk andprohibitively high costs by reason of the large volume of gas passingthrough a gas turbine and the large quantities of heat to be transferredfrom the exhaust gases to the air at rather small differences intemperature. Calculation and tests have shown that the thermo-technicalaspects of the aforesaid problem can be solved more easily by applyingthe principle of regenerative heat transfer, that is, by means of a massalternatingly absorbing and yielding heat, which mass is provided withcanals alternately traversed by two mediae, one yielding heat and theother absorbing heat. Earlier attempts to construct regenerative heatexchangers for gas turbines have not been successful due to the factthat too large a part of the feeding air was lost in the heat exchangerowing to sluicing and leakage.

Thus, a further object of the invention is to limitate the losses due tosluicing and leakage to permissible values. The attainment of thisobject presents considerable difficulties with heat exchangers for gasturbines by reason of the fact that the pressure difierence between thegas and air sides of the heat exchanger is generally in the order ofseveral atmospheres in contrast to steam installations in which thepressure difference is usually a few hundred millimeters of Watercolumn. In addition,

every percent of air leaking away constitutes a loss of power which isseveral times greater with a gas turbine than with a steam installation,partly due to the higher pressure and partly due to the larger quantityof air per Hence, the means of limiting the losses owing to sluicing andleakage as more fully described below are most important.

2,970,815 Fatented Feb. 7, 1961 The possibilities of attaining theaforesaid object are intimately connected with the possibility ofobtaining the required heat transfer with an extremely small mass provided with narrow gauge flow canals.

Other and further objects, features and advantages of the invention willbe pointed out hereinafter and set forth in the appended claims formingpart of the application.

The present application is a divisional application divided out of myprior Patent 2,836,398, issued 'May 27, 1958.

In the accompanying drawings several now preferred embodiments of theinvention are shown by way of illustration and not by way of limitation.

In the drawings:

Fig. 1 is a block diagram of an installation for a gas turbine operatedaccording to the open system and in which the air preheated by a heatexchanger according to the invention is fed to the combustion chamber.

Fig. 2 is a block diagram of an installation for a gas turbine in whichthe turbine is operated according to the closed system and in which theair preheated by the heat exchanger according to the invention is fed toa further air heater heated by an external source of heat beforereaching the turbine.

Fig. 3 is a block diagram of an open system similar to Fig. 1 but inwhich the air preheated by the heat exchanger is fed directly to theturbine, the external source of heat being located after the turbine.

Fig. 4 is a pressure-volume diagram of a turbine.

Fig. 5 is an elevational sectional view of still another modification ofa heat exchanger according to the invention.

Fig. 6 is a section taken on line 66 of Fig. 5.

Fig. 7 is a fragmentary view of a detail view of Fig. 5 on an enlargedscale, and

Fig. 8 is a graph showing the theoretical maximum efi'iciency of a heatexchanger according to the invention provided with a heat transfersurface according to Fig. 7.

Referring in detail to Figs. 1, 2 and 3, the gas turbine is operatedaccording to the so-called constant-pressure principle. In the opensystem according to Fig. 1 the turbine 1 drives a compressor 2 whichcompresses the air fed to the combustion chamber 3 with a constantpressure. The gases from the combustion chamberare fed to the turbine inwhich they perform work and are discharged through a heat exchanger 4into the open air. The heat exchanger has a gas side 4a and an air side4b and serves to transfer the heat of the exhaust gases from the turbineto the air so that the air is preheated before being fed to thecombustion chamber. in gas turbines operating with low pressure and hightemperature the major portion of the heat required for preheating theair is recovered from the exhaust gases so that only a small portion ofthe required heat must be supplied to the system from the outside bymeans of fuel as will be more fully explained hereinafter.

In the closed system according to Fig. 2, the air circulates within thesystem in a closed circuit and is again preheated in heat exchanger 4.However, before being fed to the turbine 1 it is further heated in anair heater 5 which may be a recuperative heater in which the air flowsalong one side of a heated plate or tube. Before the air from theturbine is returned to compressor 2 it must be cooled in an air cooler6. The use of the heat exchanger 4 in such a closed system has theadvantage that the amount of heat which must be delivered by the airheater '5 is reduced by therecovery of heat from the exhaust gases ofthe turbine and the amount of heat which must be removed from the systemby the cooler 6 will also be reduced. As a result, the required heattransfer surfaces in the heat exchangers 5 and 6 are reducedcorrespondingly, that is, an expensive and inefiec- 3 tive heatingsurface is replaced by an inexpensive and effective one. At the sametime fuel is saved by the recovery of heat from the air exhausted fromthe turbine.

In the open system according to Fig. 3 the combustion chamber 3 isplaced behind the turbine. Consequently, no combustion takes place aheadof the turbine and the latter is fed with air preheated in heatexchanger 4 to the temperature required for the operation of theturbine. As a result of the expansion of the heated air within theturbine, the temperature of the air decreases, heat being converted towork, and the corresponding amount of heat is added in the combustionchamber 3 which heat is produced by fuel. The heat generated in thecombustion chamber is transferred in the heat exchanger to the airflowing through the same and fed to the turbine. The advantage of thissystem is that the turbine operates with air as it does in the closedsystem of Fig. 2 and that the cooler 6 of the system of Fig. 2 is notnecessary. However, very high demands are made upon the heat exchanger.

Also the heat exchangers of Figs. 1 and 2 which recover heat from theexhaust side of the turbine must satisfy very high requirements a to thetransfer of heat. The volume or" gas leaving a gas turbine is about 3 to5 times higher than the volume of gas from the exhaust side of a steampower plant for the corresponding magnitude of the delivered power.Furthermore, the temperature of the gas coming from a gas turbine isconsiderably higher than the temperature of the exhaust gases from asteam power plant. To obtain a good fuel economy in a gas turbine it isnecessary that the greatest possible part of the high heat content ofthe exhaust gases of the turbine should be transferred to the airdelivered by the compressor. This air is heated to a, certain extent bythe compression so that its capacity of taking up additional heat fromthe exhaust gases of the turbine is correspondingly reduced.Consequently, it is desirable for a good fuel economy that the heatexchanger is capable 'of cooling the exhaust gases from the turbine to atemperature slightly higher than the temperature of the air coming fromthe compressor which air in turn should be heated to a temperature closeto the temperature of the exhaust gases from the turbine. Que of therequirements to satisfy the aforementioned conditions is to conduct thegas and the air actng upon each other in countercurrent.

The difiiculties present in the design of a heat exchanger capable ofproducing the aforementioned efiiciency of 90% under the above outlinedconditions will be further explained in connection with the diagram ofFig. 4. This figure shows a socalled pressure-volume diagram for a gasturbine operating according to the constantpressure system and appliesin principle to systems according to Figs. 1, 2 and 3. A relatively lowcompression has been selected to show that a high eiliciency can beattained by means of the heat exchanger according to the invention inspite of the low compression.

Let it be first assumed that the turbine is operated in an open systemand that the'compressor draws in air from the atmosphere at atemperature of 2l C., point A of the diagram, and that the air iscompressed to two atmospheres above atmospheric pressure so that thetotal air pressure is three atmospheres. As a result, the air is heatedin the compressor to a temperature of about 140 C., at which temperaturethe air is delivered to the combustion chamber, point B. in thecombustion chamher the temperature of the air is elevated by thecombustion of fuel to a temperature of 800 C., point C. As the result ofthe elevation of the air temperature, the volume of the air increases indirect proportion to the increase in temperature (constant-pressure),calculated in absolute temperature, so that the volumeof the air atpoint C is 2.6 times the volume of the air at point B.

The gas expands in theturbine to atmospheric pressure whereby'work isperformed in the turbine, the temperature decreasing to 550 C., point D.

The factors to be satisfied in the design of a heat exchanger for thesystems of Figs. 1 and 2 (recovery of heat from exhaust gas) which isefiicient according to the diagram of Fig. 4 shall be first analyzed. Asstated before, the heat exchanger should be capable of heating airhaving an initial temperature of 140 C. by gases having a temperature of550 C. Hence, the theoretical maximum temperature of the preheated airis 550 C., assuming an infinitely high heat transfer factor and an idealor full countercurrent, and the theoretical lowest temperature to whichthe gas can be cooled is 140 C. assuming a 100 percent efficiency of theheat exchanger.

On the basis of these figures, a heat exchanger with the desired percentefficiency will produce the following results:

Air is heated from 140 to 510 C.

Gas is cooled from 550 to 180 C.

Consequently, the total efiiciency of the power generation is raisedfrom 20 percent to 45 percent, assuming a percent combustion of thefuel, in the system ac cording to Fig. 1.

A gas turbine producing 5,000 HP. and having an eificiency of both thecompressor and the turbine of 87 percent consumes about 30 kg. of airper second at the pressure and the temperatures according to the diagramof Fig. 4. This means that a heat exchanger operating at theaforementioned ranges of temperature must transmit 10 million kcal. perhour, and this great quantity of heat must be transferred at adifference of temperature of only 40 C. between the gas and the air.

The requirements are still higher for a heat exchanger to be used in thesystem of Fig. 3 for a turbine also producing 5,000 HP. The pertinentdata are as follows:

30 kg. of air per second must be heated from to 800 C.

30 kg. of gas must be cooled per second from 840 to 180 C.

The diiference of temperature is again assumed to be 40 C. so that theefficiency of the entire system will remain the same. However, theefiiciency of the heat exchanger must be increased to 94 percent, andthe quantity or heat to be transferred is increased to 18 million kcal.per hour,

It will be clear from these examples that new ways of solving thisproblem have to be found.

According to my prior US. Patents Nos. 2,227,836 and 2,178,481 a type ofheating surface is suggested for regenerative heat exchangers in whichthe flow of gas is split up in very thin layers in a heat transfersurface provided with very narrow and short canals for instance, finemeshed wire gauze or perforated plates.

At the time when those patents were filed, gas turbines were still intheir experimental stage and not until later years gas turbines werecommercially employed. On the other-hand, the designs of theaforementioned patents could notbe applied to steam power plants as theopinion was held that the high degree of impurity of the flue gasesprevented the use of the basic features of the patents. For gas turbineshowever, owing to the great sensitivity of the turbine to impurity inthe driving gas it was necessary to use either fuels not producingappreciable impurities or thoroughly to purify the gas before feeding itto the turbine.

One of the diificulties confronting the dmigner of regenerative air'preheaters in connection with gas turbines resides in keeping air andgas apart without too great an intermixture. The aforesaid patentsdisclose regenerative heatexchangers in which'the heat transfersurfacerotates in a housing divided into two chambers, one for flue gasand one for air, every partof the heat transfer surface alternatinglypassing the gas chamber and the air chamber respectively. -Thestationary partition wall between thegas side'and the air side must notbe in contact with the rotor but acertain clearance should beleftsufiiciently' large to compensate for the deformations of the rotordue to heat expansion. For steam power plants the said clearance is notequally important, as the pressure differences between the gas side andthe air side in the heat exchanger are small compared with those of thegas turbine. With steam power plants, the pressure is calcualted inmillimeters of water column and with gas turbines in atmospheres.

In spite of the small pressure differences with steam power plants, theair leakage of the regenerative heat exchangers for this purpose is ofthe magnitude of 6 to 15 percent. A leakage of such magnitude cannot betolerated with gas turbines as it would imply too great a loss of power.A maximum leakage of 2 percent could be tolerated if the heat exchangerhas such a high degree of efficiency as the one exemplified above, andthe turbine works with high degrees of temperature.

The conditions for satisfying such high requirements are unfavorable notonly due to the great differences of pressure but also due to the hightemperature and the demands for a high degree of heat efficiency. Thehigh temperature will cause the rotor to warp-owing to the temperaturetensions, and the high degree of heat efficiency requires large heatsurfaces entailing a large rotor and great lengths of the gaps to besealed as well as a large volume of the rotor which in turn involvesthat large quantities of air will be lost by sluicing during therotation of the heat surface.

An effective heat surface permitting a radical decrease of thedimensions of the rotor is consequently not only a problem dependent onthe sealing but it is the principal requirement for reducing the lossescaused by leakage and sluicing.

Calculations have shown that by merely reducing the heating surface,leakage cannot be reduced to the degree required.

With the most common type of heat exchangers of the regenerativetypeLjungstroms air preheater-the heat transfer surface is supported bya rotor frame shaped like a wheel with plate like spokes facing withtheir edges the side surface of the wheel. Between these spokes the heattransfer surface is placed in chambers. The flow directions of air andgas are axial and opposed to each other. The rotor is carried at itscenter and slowly rotated in a housing divided into two chambers, onefor gas and one for air. Due to the counter-current, one side of therotor frame will always be in contact with the hot gas and the preheatedair while theopposite side of the rotor will always be in contact withthe cold air and the cooled gas. Owing to this fact, heat tensions willarise which will deform the rotor.

The higher the degree of efiiciency according to which the heatexchanger is to be dimensioned, the greater will be the difference intemperature between the two sides of of design is used involving quiteanother and more advantageous starting point of the solution of thesealing problem.

The basic principles employed according to the present invention may beoutlined as follows: e

The conventional rigid rotor of the heat exchanger is replaced by aflexible rotor supported on rollers. The flexibility of the rotor issuch that the rotor will always rest upon the rollers either by its ownweight or due to deformation caused by pairs of sealing rollers onopposite sides of the rotor. Consequently, tight sealing means can beprovided adjacent to the rollers and to the rotor as the position of therotor will not be altered in the proximity of the rollers by the effectof theheat.

, The rolls may in turn be made to seal also against the stationaryparts (the partition wall). This is not a difli- 6 cult problem, sincethe rolls have small sizes compared with the rotor. As they are notexposed to considerable variations in temperature, they can be mountedin housings providing a very small clearance only and they can befurther sealed by means of labyrinth sealings.

The rotor is preferably in form of a cylindrical flexible ring rotatingbetween the tight sealing means and so designed that the width of theheat transfer surface of the rotor in the direction of the flow of thegas or the air is less than 5 percent of the outer diameter of therotor, preferably between 2.5 and 0.25 percent of the diameter. As aresult, the length in the said direction of the surface to be sealedagainst the stationary parts of the heat exchangers is short whichfacilitates the sealing of the rotor. On the other hand, such a designgreatly increases the difiiculties of producing the required tremendoustransfer of heat between gas and air due to the short distance ofcoaction between air and gas. In other words, the heat transfer surfacemust be extremely effective.

The heat transfer surface of the rotor may be formed of wire gauze,perforated plates or corrugated metal strips arranged in form ofconcentric rings or continuous spirals constituting a cylindricallyshaped coil. stiffening elements for the heat transfer surface shouldthen be omitted and only ring shaped reinforcements be used. A heattransfer surface of this type may be made highly flexible and capable ofadapting itself by its own weight to the rollers.

As one side of the heat exchanger operates at very high temperatures,the sealing rolls and the support rolls for the rotor are preferablydisposed on the cold side thereof. Means of expansion may be providedbetween the hot and cold stationary parts of the heat exchanger so thattensions and stresses created in these parts by the heat are nottransferred directly to the parts of the heat exchanger supporting therotor.

According to another embodiment of the invention, a rotor is employedwhich is not only flexible but also of a compressible thickness. In thiscase pairs of sealing rolls on opposite sides of the rotor may be usedspaced so tightly that the rotor portions successively passing betweentwo rolls are compressed relative to the normal thickness of the rotorthereby obtaining a highly efiicient sealing between the gas and the airside of the heat exchanger.

A ring shaped rotor may be rotated by rollers driven by a motor. When,as sometimes can be the case, the rotor is rotated with a rather highvelocity and the gas or the air is not rotated the rotor would beretarded by the traversing air and gas.

For instance, when the peripheral velocity of the rotor is 10 meters persecond and the flow of gas and air is 60 kg. per second, the retardingperipheral force would be: I

P= l0=about 60 kg;

wherein g is the gravitational acceleration.

In case it is desirable to use a very light heat transfer surface, forinstance in turbines for airplanes which in turn requires a highvelocity of rotation, of the heating surface, the aforementioned brakingeffect can be rollers-may be dispensed with. With a system according toFig. 3 it will be possible. to use pulverized coal as fuel, as ash orother solidipa rticles of. the nstant not reach the turbine.

eliminated by imparting to, the air and gas currents a rotation in thesame direction and of the same velocity as that of the rotor.

With a sufiicient tangential velocity of the flows of air and gas, adriving force instead of a retarding one can be obtained whereby anymechanical driving of the Figs. 5" to 7 show a heat exchanger designcomprising a heat transfer means in the form of a cylindrical heattransfer ring 35 which is flexible in radial direction, and sealingbetween the gas side and the air side of the exchanger is elfected bypairs of coacting rolls.

The heating surface of this cylindrical heat transfer ring may be foundof bands wound edgewise so as to form a cylindrical coil. To facilitatesuch winding of the bands, two corrugated bands are wound. Thecorrugations are preferably so positioned that they do not run exactlyperpendicularly to the edge of the bands but somewhat diagonally acrossthe bands in such a way that the corrugations of the two bands are notparallel but cross each other to form a multitude of narrow transversepassages. The structures and theory of such flexible heat transfer meansare fully described in my aforesaid Patent 2,836,398. The corrugationtools are preferably such that the bands will be bent automaticallyabout their edges while being corrugated. This can be obtained when bymaking the corrugation flatter at one edge of a band than at theopposite edge.

The heat exchanger, as shown in Figs. and 6, comprises a casinggenerally designated by 125 in which are formed an inlet duct 126 forthe hot gas and an outlet duct 127 for the cool gas, an inlet duct 128for the cool ir and an outlet duct 129 for the hot air. Casing 125 maybe composed of two sections which are joined by a plurality of bolts andnuts 13%. The air and gas sides of the heat exchanger are separated by apartition wall 131. The heat transfer surface of the heat exchanger isformed by a rotary cylinder 132 so disposed that its wall traversescontinuously the hot and cold sides of the heat exchanger as can best beseen on Fig. 5. Cylinder 132 is supported on its cold side by aplurality of'circumferentially spaced cylindrical support rolls 133.Two'of these rolls designated by 133' are mounted within the partitionwall 131 and constitute part of the sealing means between the air sideand the gas side of the heat 'exchanger. Cylinder 132 is rotated by oneor more of the support rolls which are driven by suitable drive meansindicated as a chain drive 134.

To minimize a leakage from the high pressure air space into the lowpressure gas space at the areas at which the cylinder moves from the airspace into the gas space and vice versa, each of the rollers 133' coactswith a counter-roller 138. Rollers 138 are coupled with driven rollers133' by any suitable transmission means shown as gears 139 for rotationin unison therewith. The coacting rollers 133' and 138 are encased inhousings 14th and 141 respectively which are shaped to provide a minimumgap between the gas and air side of the heat exchanger. The rollers andtheir housings may be cooled.

Fig. 7 shows another embodiment of the heat transfer surface of thecylindrical ring 132. The heat transfer surface is built up of one ormore layers 135 of fine mesh metal gauzepreferably several layersthemeshes of which form a multitude of extremely small tortuous passagewaysor channels through the wall of the cylinder. The layers of metal gauze135' are preferably encased on both sides by perforated sheet metalplates 136 and 137. It is essential for the invention that the packagethus formed is of sufiicient radial flexibility so that it can beappreciably compressed in the direction of its thickness and that ittends to return to its initial thickness when the pressure appliedthereto is relaxed.

Fig. 7 also shows that rollers 133'- and 138 are so spaced that theminimumgap between the peripheries of the rollers is less than thenatural thickness of heat trans fer ring 132. Consequently, the wallthickness-of cylinder 132 is compressed when it passes throughtheminhmum gap formed between the two rollers. This compression closes thecylinder'wall so that in effect a seal 1 1S continuously formedbetweenlthe gas and air sidesof the heat exchanger by the successivelycompressed wall;

portions of cylinder 132.. As soon as aycylinder wall heat efliciency of100%.

portion leaves the gap between the two rollers, the inherent flexibilityof the gauze package forming the cylinder wall causes the same tore-expand and the normal channels through the cylinder wall arerestored.

The operation of the heat exchanger according to Figs. 5 to 7 will beobvious. It suffices to state that the hot gas passing from duct 126into duct 127 through the respective portion of cylinder 132 will heatthis portion, and the heat thus absorbed by the cylinder will betransferred to the air when the same passes from duct 128 into duct 129through cylinder 132.

Tests and calculations have shown that with a heat transfer surfaceconsisting of wire gauze the heat elliciency of the heat exchanger isgreatly affected by the number of layers which form the packageconstituting the wall of cylinder 132. Fig. 8 shows the theoreticalmaximum heat efficiency in percents as a function of the number oflayers forming the package. As appears from the graph of Fig. 8, theheat eificiency rises first very steeply with the number of layers andthen flattens with a rather sharp bend asymptotically toward a degree ofThe theoretically maximal degree of heat efiiciency is calculated fromthe following equation wherein n is the number of layers.

The equation gives the following values for n:

As appears from the graph and the table, the desired heat efliciency ofpercent can be obtained by 9 layers. in actual practice, a considerablygreater number of layers is required.

While the invention has been described in detail with respect to certainnow preferred examples and embodiments of the invention it will beunderstood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended,'therefore, to cover all such changes and modifications in theappended claims What is claimed as new and desired to be secured byLetters Patent is:

1. A regenerative heat exchanger for the exchange of heat between twogaseous media at different temperatures comprising first inlet conduitmeans for the hot medium, first outlet conduit means for the cooledmedium, second inlet conduit means for the cold medium to be heated,second outlet conduit means for the heated medium, heat transfer meansin the form of a cylindrical ring the peripheral walls of which areflexible in radial direction, a plurality of'cylindrical rollersrotatably mounted at the inner side of said heat transfer means andextending substantially axially across the entire length of and beingsupportingly located substantially parallel to the axis of said heattransfer means, means supporting said cylindrical rollers in positionsto support and guide said heat transfer means between the inlet conduitmeans and the outlet conduit means for said media for rotary movement ofthe, heat transfer. means about its axis, means rotating said heattransfer means so that portions of the transfer duit means, whereby thetransfer means alternately absorbs heat from the hot medium and yieldsthe absorbed heat'to the cold medium, said transfer means in'cludinga.multitude of narrow passageways extending generally in the direction ofthe flow of the media through the transfer means, and sealing meansextending substantially axially across the length of the heat transfermeans and comprising coacting members disposed on opposite sides of thewall of said heat transfer means and being in direct, closely sealingposition therewith between the first and second conduit means forimpeding leakage of the media between the first conduit means and thesecond conduit means. 1

2. A heat exchanger according to claim 1, wherein the coacting membersof said sealing means are each provided with an axially disposed rollerengaging said cylindrical ring and guiding said ring through saidmembers of the sealing means.

3. A heat exchanger according to claim 1 wherein said cylindrical ringis composed of a plurality of superimposed flexible fine mesh nettings,the mesh of the superimposed nettings forming said multitude of narrowpassageways extending generally in the direction of the flow of themedia through the cylindrical ring.

4. A regenerative heat exchanger for the exchange of heat between twogaseous media at different temperatures, said exchanger comprising firstinlet conduit means for the hot medium, first outlet conduit means forthe cooled medium, second inlet conduit means for the cold medium to beheated, second outlet conduit means for the heated medium, heat transfermeans in the form of a cylindrical ring the peripheral walls of whichare flexible in radial direction, said ring being rotatably mounted andinterposed between the inlet conduit means and the outlet conduit meansof the first and second conduit means respectively so that portions ofthe transfer ring alternately pass between the first and second conduitmeans upon rotation of the transfer ring whereby said transfer ringalternately absorbs heat from the hot medium and transmits the absorbedheat to the cold medium, said transfer ring including a multitude ofnarrow passageways extending generally in the direction of the flow ofthe media through the ring, support means supporting said heat transferring movable relative thereto, said support means being in the form ofrollers radially disposed relative to the rotational axis of said ringand supporting said ring thereon, sealing means disposed in sealingrelationship with the radially flexible heat transfer ring be tween thefirst and second conduit means for impeding a leakage of the mediabetween the first conduit means and the second conduit means, anddeflection means disposed within said conduit means in a spatial angularrelationship relative to the heat transfer ring such that a flow of amedium through the conduit means impinging upon the heat transfer ringimparts rotation to the latter.

5. A regenerative heat exchanger for the exchange of heat between twogaseous media at different temperatures, said exchanger comprising firstinlet conduit means for the hot medium, first outlet conduit means forthe cooled medium, second inlet conduit means for the cold medium to beheated, second outlet conduit means for the heated medium, flexibletransfer means movably mounted and interposed between the inlet conduitmeans and the outlet conduit means of the first and second conduit meansrespectively so that portions of said heat transfer means alternatelypass between the first and second conduit means upon movement of thetransfer means whereby said transfer means alternately absorb heat fromthe hot medium and transfer the absorbed heat to the cold medium, saidheat transfer means comprising a cylindrical ring composed of aplurality of coaxial flexible fine mesh nettings, the peripheral wallsof the ring being radially flexible and the meshes of the nettingsforming a multitude of narrow passageways extending generally in thedirection of the flow of the media through the transfer means, supportmeans supporting said transfer ring movable relative thereto, andsealing means disposed in sealing relationship withthe heat transferring between the first and second conduit means for impeding a leakageof the media between the first conduit means and.

the second conduit means, said support means and said sealing means forsaid heat transfer ring including pairs of coacting rotary guide rollersguiding therebetween the heat transfer ring and separating the conduitmeans for the hot medium and the conduit means for the medium to beheated, the coacting guide rollers of each pair being spaced from eachother by a distance slightly less than the total radial thickness ofsaid nettings for cor respondingly compressing said nettings when andwhile passing between said guide rollers thereby effecting seals betweenthe conduit means for the medium to be heated and the conduit means forthe hot medium.

References Qited in the file of this patent UNITED STATES PATENTS2,119,907 Dunlap June 7, 1938 2,227,836 Linderoth Jan. 7, 1941 2,236,635Young et al. Apr. 1, 1941 2,665,118 Broman Jan. 5, 1957 FOREIGN PATENTS651,771 Great Britain Aug. 11, 1951

